Use spans of std::byte in serialize

This switches .read() and .write() to take spans of bytes.

26 files changed, 195 insertions, 184 deletions

diff --git a/src/bench/checkblock.cpp b/src/bench/checkblock.cpp
index a9f3f5f84d..52e5cb743f 100644
--- a/src/bench/checkblock.cpp
+++ b/src/bench/checkblock.cpp
@@ -17,8 +17,8 @@
 static void DeserializeBlockTest(benchmark::Bench& bench)
 {
     CDataStream stream(benchmark::data::block413567, SER_NETWORK, PROTOCOL_VERSION);
-    char a = '\0';
-    stream.write(&a, 1); // Prevent compaction
+    std::byte a{0};
+    stream.write({&a, 1}); // Prevent compaction
 
     bench.unit("block").run([&] {
         CBlock block;
@@ -31,8 +31,8 @@ static void DeserializeBlockTest(benchmark::Bench& bench)
 static void DeserializeAndCheckBlockTest(benchmark::Bench& bench)
 {
     CDataStream stream(benchmark::data::block413567, SER_NETWORK, PROTOCOL_VERSION);
-    char a = '\0';
-    stream.write(&a, 1); // Prevent compaction
+    std::byte a{0};
+    stream.write({&a, 1}); // Prevent compaction
 
     ArgsManager bench_args;
     const auto chainParams = CreateChainParams(bench_args, CBaseChainParams::MAIN);
diff --git a/src/bench/rpc_blockchain.cpp b/src/bench/rpc_blockchain.cpp
index 9bc31461d2..2143bcf950 100644
--- a/src/bench/rpc_blockchain.cpp
+++ b/src/bench/rpc_blockchain.cpp
@@ -23,8 +23,8 @@ struct TestBlockAndIndex {
     TestBlockAndIndex()
     {
         CDataStream stream(benchmark::data::block413567, SER_NETWORK, PROTOCOL_VERSION);
-        char a = '\0';
-        stream.write(&a, 1); // Prevent compaction
+        std::byte a{0};
+        stream.write({&a, 1}); // Prevent compaction
 
         stream >> block;
 
diff --git a/src/common/bloom.cpp b/src/common/bloom.cpp
index c3603b5d2a..a6531b90b3 100644
--- a/src/common/bloom.cpp
+++ b/src/common/bloom.cpp
@@ -61,7 +61,7 @@ void CBloomFilter::insert(const COutPoint& outpoint)
 {
     CDataStream stream(SER_NETWORK, PROTOCOL_VERSION);
     stream << outpoint;
-    insert(stream);
+    insert(MakeUCharSpan(stream));
 }
 
 bool CBloomFilter::contains(Span<const unsigned char> vKey) const
@@ -82,7 +82,7 @@ bool CBloomFilter::contains(const COutPoint& outpoint) const
 {
     CDataStream stream(SER_NETWORK, PROTOCOL_VERSION);
     stream << outpoint;
-    return contains(stream);
+    return contains(MakeUCharSpan(stream));
 }
 
 bool CBloomFilter::IsWithinSizeConstraints() const
diff --git a/src/dbwrapper.h b/src/dbwrapper.h
index 12db0fffcc..1109cb5888 100644
--- a/src/dbwrapper.h
+++ b/src/dbwrapper.h
@@ -147,7 +147,7 @@ public:
     template<typename K> bool GetKey(K& key) {
         leveldb::Slice slKey = piter->key();
         try {
-            CDataStream ssKey(MakeUCharSpan(slKey), SER_DISK, CLIENT_VERSION);
+            CDataStream ssKey{MakeByteSpan(slKey), SER_DISK, CLIENT_VERSION};
             ssKey >> key;
         } catch (const std::exception&) {
             return false;
@@ -158,7 +158,7 @@ public:
     template<typename V> bool GetValue(V& value) {
         leveldb::Slice slValue = piter->value();
         try {
-            CDataStream ssValue(MakeUCharSpan(slValue), SER_DISK, CLIENT_VERSION);
+            CDataStream ssValue{MakeByteSpan(slValue), SER_DISK, CLIENT_VERSION};
             ssValue.Xor(dbwrapper_private::GetObfuscateKey(parent));
             ssValue >> value;
         } catch (const std::exception&) {
@@ -244,7 +244,7 @@ public:
             dbwrapper_private::HandleError(status);
         }
         try {
-            CDataStream ssValue(MakeUCharSpan(strValue), SER_DISK, CLIENT_VERSION);
+            CDataStream ssValue{MakeByteSpan(strValue), SER_DISK, CLIENT_VERSION};
             ssValue.Xor(obfuscate_key);
             ssValue >> value;
         } catch (const std::exception&) {
diff --git a/src/hash.h b/src/hash.h
index 1456a899d8..9f582842c1 100644
--- a/src/hash.h
+++ b/src/hash.h
@@ -111,8 +111,9 @@ public:
     int GetType() const { return nType; }
     int GetVersion() const { return nVersion; }
 
-    void write(const char *pch, size_t size) {
-        ctx.Write((const unsigned char*)pch, size);
+    void write(Span<const std::byte> src)
+    {
+        ctx.Write(UCharCast(src.data()), src.size());
     }
 
     /** Compute the double-SHA256 hash of all data written to this object.
@@ -162,18 +163,18 @@ private:
 public:
     explicit CHashVerifier(Source* source_) : CHashWriter(source_->GetType(), source_->GetVersion()), source(source_) {}
 
-    void read(char* pch, size_t nSize)
+    void read(Span<std::byte> dst)
     {
-        source->read(pch, nSize);
-        this->write(pch, nSize);
+        source->read(dst);
+        this->write(dst);
     }
 
     void ignore(size_t nSize)
     {
-        char data[1024];
+        std::byte data[1024];
         while (nSize > 0) {
             size_t now = std::min<size_t>(nSize, 1024);
-            read(data, now);
+            read({data, now});
             nSize -= now;
         }
     }
diff --git a/src/net.cpp b/src/net.cpp
index 019e77fd7a..9c78977700 100644
--- a/src/net.cpp
+++ b/src/net.cpp
@@ -3120,11 +3120,11 @@ void CaptureMessage(const CAddress& addr, const std::string& msg_type, const Spa
     CAutoFile f(fsbridge::fopen(path, "ab"), SER_DISK, CLIENT_VERSION);
 
     ser_writedata64(f, now.count());
-    f.write(msg_type.data(), msg_type.length());
+    f.write(MakeByteSpan(msg_type));
     for (auto i = msg_type.length(); i < CMessageHeader::COMMAND_SIZE; ++i) {
         f << uint8_t{'\0'};
     }
     uint32_t size = data.size();
     ser_writedata32(f, size);
-    f.write((const char*)data.data(), data.size());
+    f.write(AsBytes(data));
 }
diff --git a/src/node/blockstorage.cpp b/src/node/blockstorage.cpp
index 53bc2b5069..16f6ce0a21 100644
--- a/src/node/blockstorage.cpp
+++ b/src/node/blockstorage.cpp
@@ -435,7 +435,7 @@ bool ReadRawBlockFromDisk(std::vector<uint8_t>& block, const FlatFilePos& pos, c
         }
 
         block.resize(blk_size); // Zeroing of memory is intentional here
-        filein.read((char*)block.data(), blk_size);
+        filein.read(MakeWritableByteSpan(block));
     } catch (const std::exception& e) {
         return error("%s: Read from block file failed: %s for %s", __func__, e.what(), pos.ToString());
     }
diff --git a/src/psbt.cpp b/src/psbt.cpp
index 8248609ba6..c8c73e130b 100644
--- a/src/psbt.cpp
+++ b/src/psbt.cpp
@@ -399,7 +399,7 @@ bool DecodeBase64PSBT(PartiallySignedTransaction& psbt, const std::string& base6
 
 bool DecodeRawPSBT(PartiallySignedTransaction& psbt, const std::string& tx_data, std::string& error)
 {
-    CDataStream ss_data(MakeUCharSpan(tx_data), SER_NETWORK, PROTOCOL_VERSION);
+    CDataStream ss_data(MakeByteSpan(tx_data), SER_NETWORK, PROTOCOL_VERSION);
     try {
         ss_data >> psbt;
         if (!ss_data.empty()) {
diff --git a/src/pubkey.h b/src/pubkey.h
index 349081205b..dfe06f834c 100644
--- a/src/pubkey.h
+++ b/src/pubkey.h
@@ -142,14 +142,14 @@ public:
     {
         unsigned int len = size();
         ::WriteCompactSize(s, len);
-        s.write((char*)vch, len);
+        s.write(AsBytes(Span{vch, len}));
     }
     template <typename Stream>
     void Unserialize(Stream& s)
     {
         const unsigned int len(::ReadCompactSize(s));
         if (len <= SIZE) {
-            s.read((char*)vch, len);
+            s.read(AsWritableBytes(Span{vch, len}));
             if (len != size()) {
                 Invalidate();
             }
diff --git a/src/script/bitcoinconsensus.cpp b/src/script/bitcoinconsensus.cpp
index dd15e6104c..f7f9dfc262 100644
--- a/src/script/bitcoinconsensus.cpp
+++ b/src/script/bitcoinconsensus.cpp
@@ -22,20 +22,23 @@ public:
     m_remaining(txToLen)
     {}
 
-    void read(char* pch, size_t nSize)
+    void read(Span<std::byte> dst)
     {
-        if (nSize > m_remaining)
+        if (dst.size() > m_remaining) {
             throw std::ios_base::failure(std::string(__func__) + ": end of data");
+        }
 
-        if (pch == nullptr)
+        if (dst.data() == nullptr) {
             throw std::ios_base::failure(std::string(__func__) + ": bad destination buffer");
+        }
 
-        if (m_data == nullptr)
+        if (m_data == nullptr) {
             throw std::ios_base::failure(std::string(__func__) + ": bad source buffer");
+        }
 
-        memcpy(pch, m_data, nSize);
-        m_remaining -= nSize;
-        m_data += nSize;
+        memcpy(dst.data(), m_data, dst.size());
+        m_remaining -= dst.size();
+        m_data += dst.size();
     }
 
     template<typename T>
diff --git a/src/script/interpreter.cpp b/src/script/interpreter.cpp
index 95ffe40a74..104db4b78e 100644
--- a/src/script/interpreter.cpp
+++ b/src/script/interpreter.cpp
@@ -1303,12 +1303,12 @@ public:
         it = itBegin;
         while (scriptCode.GetOp(it, opcode)) {
             if (opcode == OP_CODESEPARATOR) {
-                s.write((char*)&itBegin[0], it-itBegin-1);
+                s.write(AsBytes(Span{&itBegin[0], size_t(it - itBegin - 1)}));
                 itBegin = it;
             }
         }
         if (itBegin != scriptCode.end())
-            s.write((char*)&itBegin[0], it-itBegin);
+            s.write(AsBytes(Span{&itBegin[0], size_t(it - itBegin)}));
     }
 
     /** Serialize an input of txTo */
diff --git a/src/serialize.h b/src/serialize.h
index 4cc4b0338c..c287d3a116 100644
--- a/src/serialize.h
+++ b/src/serialize.h
@@ -47,79 +47,72 @@ static const unsigned int MAX_VECTOR_ALLOCATE = 5000000;
 struct deserialize_type {};
 constexpr deserialize_type deserialize {};
 
-//! Safely convert odd char pointer types to standard ones.
-inline char* CharCast(char* c) { return c; }
-inline char* CharCast(unsigned char* c) { return (char*)c; }
-inline const char* CharCast(const char* c) { return c; }
-inline const char* CharCast(const unsigned char* c) { return (const char*)c; }
-
 /*
  * Lowest-level serialization and conversion.
- * @note Sizes of these types are verified in the tests
  */
 template<typename Stream> inline void ser_writedata8(Stream &s, uint8_t obj)
 {
-    s.write((char*)&obj, 1);
+    s.write(AsBytes(Span{&obj, 1}));
 }
 template<typename Stream> inline void ser_writedata16(Stream &s, uint16_t obj)
 {
     obj = htole16(obj);
-    s.write((char*)&obj, 2);
+    s.write(AsBytes(Span{&obj, 1}));
 }
 template<typename Stream> inline void ser_writedata16be(Stream &s, uint16_t obj)
 {
     obj = htobe16(obj);
-    s.write((char*)&obj, 2);
+    s.write(AsBytes(Span{&obj, 1}));
 }
 template<typename Stream> inline void ser_writedata32(Stream &s, uint32_t obj)
 {
     obj = htole32(obj);
-    s.write((char*)&obj, 4);
+    s.write(AsBytes(Span{&obj, 1}));
 }
 template<typename Stream> inline void ser_writedata32be(Stream &s, uint32_t obj)
 {
     obj = htobe32(obj);
-    s.write((char*)&obj, 4);
+    s.write(AsBytes(Span{&obj, 1}));
 }
 template<typename Stream> inline void ser_writedata64(Stream &s, uint64_t obj)
 {
     obj = htole64(obj);
-    s.write((char*)&obj, 8);
+    s.write(AsBytes(Span{&obj, 1}));
 }
 template<typename Stream> inline uint8_t ser_readdata8(Stream &s)
 {
     uint8_t obj;
-    s.read((char*)&obj, 1);
+    s.read(AsWritableBytes(Span{&obj, 1}));
     return obj;
 }
 template<typename Stream> inline uint16_t ser_readdata16(Stream &s)
 {
     uint16_t obj;
-    s.read((char*)&obj, 2);
+    s.read(AsWritableBytes(Span{&obj, 1}));
     return le16toh(obj);
 }
 template<typename Stream> inline uint16_t ser_readdata16be(Stream &s)
 {
     uint16_t obj;
-    s.read((char*)&obj, 2);
+    s.read(AsWritableBytes(Span{&obj, 1}));
     return be16toh(obj);
 }
 template<typename Stream> inline uint32_t ser_readdata32(Stream &s)
 {
     uint32_t obj;
-    s.read((char*)&obj, 4);
+    s.read(AsWritableBytes(Span{&obj, 1}));
     return le32toh(obj);
 }
 template<typename Stream> inline uint32_t ser_readdata32be(Stream &s)
 {
     uint32_t obj;
-    s.read((char*)&obj, 4);
+    s.read(AsWritableBytes(Span{&obj, 1}));
     return be32toh(obj);
 }
 template<typename Stream> inline uint64_t ser_readdata64(Stream &s)
 {
     uint64_t obj;
-    s.read((char*)&obj, 8);
+    s.read(AsWritableBytes(Span{&obj, 1}));
     return le64toh(obj);
 }
 
@@ -127,7 +120,7 @@ template<typename Stream> inline uint64_t ser_readdata64(Stream &s)
 /////////////////////////////////////////////////////////////////
 //
 // Templates for serializing to anything that looks like a stream,
-// i.e. anything that supports .read(char*, size_t) and .write(char*, size_t)
+// i.e. anything that supports .read(Span<std::byte>) and .write(Span<const std::byte>)
 //
 
 class CSizeComputer;
@@ -206,10 +199,10 @@ template<typename Stream> inline void Serialize(Stream& s, int32_t a ) { ser_wri
 template<typename Stream> inline void Serialize(Stream& s, uint32_t a) { ser_writedata32(s, a); }
 template<typename Stream> inline void Serialize(Stream& s, int64_t a ) { ser_writedata64(s, a); }
 template<typename Stream> inline void Serialize(Stream& s, uint64_t a) { ser_writedata64(s, a); }
-template<typename Stream, int N> inline void Serialize(Stream& s, const char (&a)[N]) { s.write(a, N); }
-template<typename Stream, int N> inline void Serialize(Stream& s, const unsigned char (&a)[N]) { s.write(CharCast(a), N); }
-template<typename Stream> inline void Serialize(Stream& s, const Span<const unsigned char>& span) { s.write(CharCast(span.data()), span.size()); }
-template<typename Stream> inline void Serialize(Stream& s, const Span<unsigned char>& span) { s.write(CharCast(span.data()), span.size()); }
+template<typename Stream, int N> inline void Serialize(Stream& s, const char (&a)[N]) { s.write(MakeByteSpan(a)); }
+template<typename Stream, int N> inline void Serialize(Stream& s, const unsigned char (&a)[N]) { s.write(MakeByteSpan(a)); }
+template<typename Stream> inline void Serialize(Stream& s, const Span<const unsigned char>& span) { s.write(AsBytes(span)); }
+template<typename Stream> inline void Serialize(Stream& s, const Span<unsigned char>& span) { s.write(AsBytes(span)); }
 
 #ifndef CHAR_EQUALS_INT8
 template<typename Stream> inline void Unserialize(Stream& s, char& a    ) { a = ser_readdata8(s); } // TODO Get rid of bare char
@@ -222,9 +215,9 @@ template<typename Stream> inline void Unserialize(Stream& s, int32_t& a ) { a =
 template<typename Stream> inline void Unserialize(Stream& s, uint32_t& a) { a = ser_readdata32(s); }
 template<typename Stream> inline void Unserialize(Stream& s, int64_t& a ) { a = ser_readdata64(s); }
 template<typename Stream> inline void Unserialize(Stream& s, uint64_t& a) { a = ser_readdata64(s); }
-template<typename Stream, int N> inline void Unserialize(Stream& s, char (&a)[N]) { s.read(a, N); }
-template<typename Stream, int N> inline void Unserialize(Stream& s, unsigned char (&a)[N]) { s.read(CharCast(a), N); }
-template<typename Stream> inline void Unserialize(Stream& s, Span<unsigned char>& span) { s.read(CharCast(span.data()), span.size()); }
+template<typename Stream, int N> inline void Unserialize(Stream& s, char (&a)[N]) { s.read(MakeWritableByteSpan(a)); }
+template<typename Stream, int N> inline void Unserialize(Stream& s, unsigned char (&a)[N]) { s.read(MakeWritableByteSpan(a)); }
+template<typename Stream> inline void Unserialize(Stream& s, Span<unsigned char>& span) { s.read(AsWritableBytes(span)); }
 
 template <typename Stream> inline void Serialize(Stream& s, bool a) { uint8_t f = a; ser_writedata8(s, f); }
 template <typename Stream> inline void Unserialize(Stream& s, bool& a) { uint8_t f = ser_readdata8(s); a = f; }
@@ -479,10 +472,10 @@ struct CustomUintFormatter
         if (v < 0 || v > MAX) throw std::ios_base::failure("CustomUintFormatter value out of range");
         if (BigEndian) {
             uint64_t raw = htobe64(v);
-            s.write(((const char*)&raw) + 8 - Bytes, Bytes);
+            s.write({BytePtr(&raw) + 8 - Bytes, Bytes});
         } else {
             uint64_t raw = htole64(v);
-            s.write((const char*)&raw, Bytes);
+            s.write({BytePtr(&raw), Bytes});
         }
     }
 
@@ -492,10 +485,10 @@ struct CustomUintFormatter
         static_assert(std::numeric_limits<U>::max() >= MAX && std::numeric_limits<U>::min() <= 0, "Assigned type too small");
         uint64_t raw = 0;
         if (BigEndian) {
-            s.read(((char*)&raw) + 8 - Bytes, Bytes);
+            s.read({BytePtr(&raw) + 8 - Bytes, Bytes});
             v = static_cast<I>(be64toh(raw));
         } else {
-            s.read((char*)&raw, Bytes);
+            s.read({BytePtr(&raw), Bytes});
             v = static_cast<I>(le64toh(raw));
         }
     }
@@ -551,7 +544,7 @@ struct LimitedStringFormatter
             throw std::ios_base::failure("String length limit exceeded");
         }
         v.resize(size);
-        if (size != 0) s.read((char*)v.data(), size);
+        if (size != 0) s.read(MakeWritableByteSpan(v));
     }
 
     template<typename Stream>
@@ -715,7 +708,7 @@ void Serialize(Stream& os, const std::basic_string<C>& str)
 {
     WriteCompactSize(os, str.size());
     if (!str.empty())
-        os.write((char*)str.data(), str.size() * sizeof(C));
+        os.write(MakeByteSpan(str));
 }
 
 template<typename Stream, typename C>
@@ -724,7 +717,7 @@ void Unserialize(Stream& is, std::basic_string<C>& str)
     unsigned int nSize = ReadCompactSize(is);
     str.resize(nSize);
     if (nSize != 0)
-        is.read((char*)str.data(), nSize * sizeof(C));
+        is.read(MakeWritableByteSpan(str));
 }
 
 
@@ -737,7 +730,7 @@ void Serialize_impl(Stream& os, const prevector<N, T>& v, const unsigned char&)
 {
     WriteCompactSize(os, v.size());
     if (!v.empty())
-        os.write((char*)v.data(), v.size() * sizeof(T));
+        os.write(MakeByteSpan(v));
 }
 
 template<typename Stream, unsigned int N, typename T, typename V>
@@ -764,7 +757,7 @@ void Unserialize_impl(Stream& is, prevector<N, T>& v, const unsigned char&)
     {
         unsigned int blk = std::min(nSize - i, (unsigned int)(1 + 4999999 / sizeof(T)));
         v.resize_uninitialized(i + blk);
-        is.read((char*)&v[i], blk * sizeof(T));
+        is.read(AsWritableBytes(Span{&v[i], blk}));
         i += blk;
     }
 }
@@ -791,7 +784,7 @@ void Serialize_impl(Stream& os, const std::vector<T, A>& v, const unsigned char&
 {
     WriteCompactSize(os, v.size());
     if (!v.empty())
-        os.write((char*)v.data(), v.size() * sizeof(T));
+        os.write(MakeByteSpan(v));
 }
 
 template<typename Stream, typename T, typename A>
@@ -830,7 +823,7 @@ void Unserialize_impl(Stream& is, std::vector<T, A>& v, const unsigned char&)
     {
         unsigned int blk = std::min(nSize - i, (unsigned int)(1 + 4999999 / sizeof(T)));
         v.resize(i + blk);
-        is.read((char*)&v[i], blk * sizeof(T));
+        is.read(AsWritableBytes(Span{&v[i], blk}));
         i += blk;
     }
 }
@@ -995,9 +988,9 @@ protected:
 public:
     explicit CSizeComputer(int nVersionIn) : nSize(0), nVersion(nVersionIn) {}
 
-    void write(const char *psz, size_t _nSize)
+    void write(Span<const std::byte> src)
     {
-        this->nSize += _nSize;
+        this->nSize += src.size();
     }
 
     /** Pretend _nSize bytes are written, without specifying them. */
diff --git a/src/streams.h b/src/streams.h
index 384bb632b0..2f26be6dd8 100644
--- a/src/streams.h
+++ b/src/streams.h
@@ -49,14 +49,14 @@ public:
         return (*this);
     }
 
-    void write(const char* pch, size_t nSize)
+    void write(Span<const std::byte> src)
     {
-        stream->write(pch, nSize);
+        stream->write(src);
     }
 
-    void read(char* pch, size_t nSize)
+    void read(Span<std::byte> dst)
     {
-        stream->read(pch, nSize);
+        stream->read(dst);
     }
 
     int GetVersion() const { return nVersion; }
@@ -94,17 +94,17 @@ class CVectorWriter
     {
         ::SerializeMany(*this, std::forward<Args>(args)...);
     }
-    void write(const char* pch, size_t nSize)
+    void write(Span<const std::byte> src)
     {
         assert(nPos <= vchData.size());
-        size_t nOverwrite = std::min(nSize, vchData.size() - nPos);
+        size_t nOverwrite = std::min(src.size(), vchData.size() - nPos);
         if (nOverwrite) {
-            memcpy(vchData.data() + nPos, reinterpret_cast<const unsigned char*>(pch), nOverwrite);
+            memcpy(vchData.data() + nPos, src.data(), nOverwrite);
         }
-        if (nOverwrite < nSize) {
-            vchData.insert(vchData.end(), reinterpret_cast<const unsigned char*>(pch) + nOverwrite, reinterpret_cast<const unsigned char*>(pch) + nSize);
+        if (nOverwrite < src.size()) {
+            vchData.insert(vchData.end(), UCharCast(src.data()) + nOverwrite, UCharCast(src.end()));
         }
-        nPos += nSize;
+        nPos += src.size();
     }
     template<typename T>
     CVectorWriter& operator<<(const T& obj)
@@ -161,18 +161,18 @@ public:
     size_t size() const { return m_data.size(); }
     bool empty() const { return m_data.empty(); }
 
-    void read(char* dst, size_t n)
+    void read(Span<std::byte> dst)
     {
-        if (n == 0) {
+        if (dst.size() == 0) {
             return;
         }
 
         // Read from the beginning of the buffer
-        if (n > m_data.size()) {
+        if (dst.size() > m_data.size()) {
             throw std::ios_base::failure("SpanReader::read(): end of data");
         }
-        memcpy(dst, m_data.data(), n);
-        m_data = m_data.subspan(n);
+        memcpy(dst.data(), m_data.data(), dst.size());
+        m_data = m_data.subspan(dst.size());
     }
 };
 
@@ -206,6 +206,7 @@ public:
         : nType{nTypeIn},
           nVersion{nVersionIn} {}
 
+    explicit CDataStream(Span<const uint8_t> sp, int type, int version) : CDataStream{AsBytes(sp), type, version} {}
     explicit CDataStream(Span<const value_type> sp, int nTypeIn, int nVersionIn)
         : vch(sp.data(), sp.data() + sp.size()),
           nType{nTypeIn},
@@ -221,7 +222,7 @@ public:
 
     std::string str() const
     {
-        return (std::string(begin(), end()));
+        return std::string{UCharCast(data()), UCharCast(data() + size())};
     }
 
 
@@ -342,16 +343,16 @@ public:
     void SetVersion(int n)       { nVersion = n; }
     int GetVersion() const       { return nVersion; }
 
-    void read(char* pch, size_t nSize)
+    void read(Span<value_type> dst)
     {
-        if (nSize == 0) return;
+        if (dst.size() == 0) return;
 
         // Read from the beginning of the buffer
-        unsigned int nReadPosNext = nReadPos + nSize;
+        unsigned int nReadPosNext = nReadPos + dst.size();
         if (nReadPosNext > vch.size()) {
             throw std::ios_base::failure("CDataStream::read(): end of data");
         }
-        memcpy(pch, &vch[nReadPos], nSize);
+        memcpy(dst.data(), &vch[nReadPos], dst.size());
         if (nReadPosNext == vch.size())
         {
             nReadPos = 0;
@@ -379,10 +380,10 @@ public:
         nReadPos = nReadPosNext;
     }
 
-    void write(const char* pch, size_t nSize)
+    void write(Span<const value_type> src)
     {
         // Write to the end of the buffer
-        vch.insert(vch.end(), pch, pch + nSize);
+        vch.insert(vch.end(), src.begin(), src.end());
     }
 
     template<typename Stream>
@@ -390,7 +391,7 @@ public:
     {
         // Special case: stream << stream concatenates like stream += stream
         if (!vch.empty())
-            s.write((char*)vch.data(), vch.size() * sizeof(value_type));
+            s.write(MakeByteSpan(vch));
     }
 
     template<typename T>
@@ -421,7 +422,7 @@ public:
         }
 
         for (size_type i = 0, j = 0; i != size(); i++) {
-            vch[i] ^= key[j++];
+            vch[i] ^= std::byte{key[j++]};
 
             // This potentially acts on very many bytes of data, so it's
             // important that we calculate `j`, i.e. the `key` index in this
@@ -594,12 +595,13 @@ public:
     int GetType() const          { return nType; }
     int GetVersion() const       { return nVersion; }
 
-    void read(char* pch, size_t nSize)
+    void read(Span<std::byte> dst)
     {
         if (!file)
             throw std::ios_base::failure("CAutoFile::read: file handle is nullptr");
-        if (fread(pch, 1, nSize, file) != nSize)
+        if (fread(dst.data(), 1, dst.size(), file) != dst.size()) {
             throw std::ios_base::failure(feof(file) ? "CAutoFile::read: end of file" : "CAutoFile::read: fread failed");
+        }
     }
 
     void ignore(size_t nSize)
@@ -615,12 +617,13 @@ public:
         }
     }
 
-    void write(const char* pch, size_t nSize)
+    void write(Span<const std::byte> src)
     {
         if (!file)
             throw std::ios_base::failure("CAutoFile::write: file handle is nullptr");
-        if (fwrite(pch, 1, nSize, file) != nSize)
+        if (fwrite(src.data(), 1, src.size(), file) != src.size()) {
             throw std::ios_base::failure("CAutoFile::write: write failed");
+        }
     }
 
     template<typename T>
@@ -661,7 +664,7 @@ private:
     uint64_t nReadPos;    //!< how many bytes have been read from this
     uint64_t nReadLimit;  //!< up to which position we're allowed to read
     uint64_t nRewind;     //!< how many bytes we guarantee to rewind
-    std::vector<char> vchBuf; //!< the buffer
+    std::vector<std::byte> vchBuf; //!< the buffer
 
 protected:
     //! read data from the source to fill the buffer
@@ -682,8 +685,8 @@ protected:
     }
 
 public:
-    CBufferedFile(FILE *fileIn, uint64_t nBufSize, uint64_t nRewindIn, int nTypeIn, int nVersionIn) :
-        nType(nTypeIn), nVersion(nVersionIn), nSrcPos(0), nReadPos(0), nReadLimit(std::numeric_limits<uint64_t>::max()), nRewind(nRewindIn), vchBuf(nBufSize, 0)
+    CBufferedFile(FILE* fileIn, uint64_t nBufSize, uint64_t nRewindIn, int nTypeIn, int nVersionIn)
+        : nType(nTypeIn), nVersion(nVersionIn), nSrcPos(0), nReadPos(0), nReadLimit(std::numeric_limits<uint64_t>::max()), nRewind(nRewindIn), vchBuf(nBufSize, std::byte{0})
     {
         if (nRewindIn >= nBufSize)
             throw std::ios_base::failure("Rewind limit must be less than buffer size");
@@ -716,22 +719,23 @@ public:
     }
 
     //! read a number of bytes
-    void read(char *pch, size_t nSize) {
-        if (nSize + nReadPos > nReadLimit)
+    void read(Span<std::byte> dst)
+    {
+        if (dst.size() + nReadPos > nReadLimit) {
             throw std::ios_base::failure("Read attempted past buffer limit");
-        while (nSize > 0) {
+        }
+        while (dst.size() > 0) {
             if (nReadPos == nSrcPos)
                 Fill();
             unsigned int pos = nReadPos % vchBuf.size();
-            size_t nNow = nSize;
+            size_t nNow = dst.size();
             if (nNow + pos > vchBuf.size())
                 nNow = vchBuf.size() - pos;
             if (nNow + nReadPos > nSrcPos)
                 nNow = nSrcPos - nReadPos;
-            memcpy(pch, &vchBuf[pos], nNow);
+            memcpy(dst.data(), &vchBuf[pos], nNow);
             nReadPos += nNow;
-            pch += nNow;
-            nSize -= nNow;
+            dst = dst.subspan(nNow);
         }
     }
 
@@ -774,12 +778,14 @@ public:
     }
 
     //! search for a given byte in the stream, and remain positioned on it
-    void FindByte(char ch) {
+    void FindByte(uint8_t ch)
+    {
         while (true) {
             if (nReadPos == nSrcPos)
                 Fill();
-            if (vchBuf[nReadPos % vchBuf.size()] == ch)
+            if (vchBuf[nReadPos % vchBuf.size()] == std::byte{ch}) {
                 break;
+            }
             nReadPos++;
         }
     }
diff --git a/src/support/allocators/zeroafterfree.h b/src/support/allocators/zeroafterfree.h
index bc9c95eb53..0befe0ffcd 100644
--- a/src/support/allocators/zeroafterfree.h
+++ b/src/support/allocators/zeroafterfree.h
@@ -41,6 +41,6 @@ struct zero_after_free_allocator : public std::allocator<T> {
 };
 
 /** Byte-vector that clears its contents before deletion. */
-using SerializeData = std::vector<uint8_t, zero_after_free_allocator<uint8_t>>;
+using SerializeData = std::vector<std::byte, zero_after_free_allocator<std::byte>>;
 
 #endif // BITCOIN_SUPPORT_ALLOCATORS_ZEROAFTERFREE_H
diff --git a/src/test/bloom_tests.cpp b/src/test/bloom_tests.cpp
index bd579db205..35c4108caa 100644
--- a/src/test/bloom_tests.cpp
+++ b/src/test/bloom_tests.cpp
@@ -43,8 +43,9 @@ BOOST_AUTO_TEST_CASE(bloom_create_insert_serialize)
     stream << filter;
 
     std::vector<uint8_t> expected = ParseHex("03614e9b050000000000000001");
+    auto result{MakeUCharSpan(stream)};
 
-    BOOST_CHECK_EQUAL_COLLECTIONS(stream.begin(), stream.end(), expected.begin(), expected.end());
+    BOOST_CHECK_EQUAL_COLLECTIONS(result.begin(), result.end(), expected.begin(), expected.end());
 
     BOOST_CHECK_MESSAGE( filter.contains(ParseHex("99108ad8ed9bb6274d3980bab5a85c048f0950c8")), "Bloom filter doesn't contain just-inserted object!");
 }
@@ -69,8 +70,9 @@ BOOST_AUTO_TEST_CASE(bloom_create_insert_serialize_with_tweak)
     stream << filter;
 
     std::vector<uint8_t> expected = ParseHex("03ce4299050000000100008001");
+    auto result{MakeUCharSpan(stream)};
 
-    BOOST_CHECK_EQUAL_COLLECTIONS(stream.begin(), stream.end(), expected.begin(), expected.end());
+    BOOST_CHECK_EQUAL_COLLECTIONS(result.begin(), result.end(), expected.begin(), expected.end());
 }
 
 BOOST_AUTO_TEST_CASE(bloom_create_insert_key)
@@ -89,8 +91,9 @@ BOOST_AUTO_TEST_CASE(bloom_create_insert_key)
     stream << filter;
 
     std::vector<unsigned char> expected = ParseHex("038fc16b080000000000000001");
+    auto result{MakeUCharSpan(stream)};
 
-    BOOST_CHECK_EQUAL_COLLECTIONS(stream.begin(), stream.end(), expected.begin(), expected.end());
+    BOOST_CHECK_EQUAL_COLLECTIONS(result.begin(), result.end(), expected.begin(), expected.end());
 }
 
 BOOST_AUTO_TEST_CASE(bloom_match)
@@ -341,8 +344,9 @@ BOOST_AUTO_TEST_CASE(merkle_block_3_and_serialize)
     merkleStream << merkleBlock;
 
     std::vector<uint8_t> expected = ParseHex("0100000079cda856b143d9db2c1caff01d1aecc8630d30625d10e8b4b8b0000000000000b50cc069d6a3e33e3ff84a5c41d9d3febe7c770fdcc96b2c3ff60abe184f196367291b4d4c86041b8fa45d630100000001b50cc069d6a3e33e3ff84a5c41d9d3febe7c770fdcc96b2c3ff60abe184f19630101");
+    auto result{MakeUCharSpan(merkleStream)};
 
-    BOOST_CHECK_EQUAL_COLLECTIONS(expected.begin(), expected.end(), merkleStream.begin(), merkleStream.end());
+    BOOST_CHECK_EQUAL_COLLECTIONS(expected.begin(), expected.end(), result.begin(), result.end());
 }
 
 BOOST_AUTO_TEST_CASE(merkle_block_4)
diff --git a/src/test/fuzz/autofile.cpp b/src/test/fuzz/autofile.cpp
index 0cc2d12d29..3b410930ed 100644
--- a/src/test/fuzz/autofile.cpp
+++ b/src/test/fuzz/autofile.cpp
@@ -23,16 +23,16 @@ FUZZ_TARGET(autofile)
         CallOneOf(
             fuzzed_data_provider,
             [&] {
-                std::array<uint8_t, 4096> arr{};
+                std::array<std::byte, 4096> arr{};
                 try {
-                    auto_file.read((char*)arr.data(), fuzzed_data_provider.ConsumeIntegralInRange<size_t>(0, 4096));
+                    auto_file.read({arr.data(), fuzzed_data_provider.ConsumeIntegralInRange<size_t>(0, 4096)});
                 } catch (const std::ios_base::failure&) {
                 }
             },
             [&] {
-                const std::array<uint8_t, 4096> arr{};
+                const std::array<std::byte, 4096> arr{};
                 try {
-                    auto_file.write((const char*)arr.data(), fuzzed_data_provider.ConsumeIntegralInRange<size_t>(0, 4096));
+                    auto_file.write({arr.data(), fuzzed_data_provider.ConsumeIntegralInRange<size_t>(0, 4096)});
                 } catch (const std::ios_base::failure&) {
                 }
             },
diff --git a/src/test/fuzz/buffered_file.cpp b/src/test/fuzz/buffered_file.cpp
index c3c2e4050f..a8c3318629 100644
--- a/src/test/fuzz/buffered_file.cpp
+++ b/src/test/fuzz/buffered_file.cpp
@@ -33,9 +33,9 @@ FUZZ_TARGET(buffered_file)
             CallOneOf(
                 fuzzed_data_provider,
                 [&] {
-                    std::array<uint8_t, 4096> arr{};
+                    std::array<std::byte, 4096> arr{};
                     try {
-                        opt_buffered_file->read((char*)arr.data(), fuzzed_data_provider.ConsumeIntegralInRange<size_t>(0, 4096));
+                        opt_buffered_file->read({arr.data(), fuzzed_data_provider.ConsumeIntegralInRange<size_t>(0, 4096)});
                     } catch (const std::ios_base::failure&) {
                     }
                 },
@@ -53,7 +53,7 @@ FUZZ_TARGET(buffered_file)
                         return;
                     }
                     try {
-                        opt_buffered_file->FindByte(fuzzed_data_provider.ConsumeIntegral<char>());
+                        opt_buffered_file->FindByte(fuzzed_data_provider.ConsumeIntegral<uint8_t>());
                     } catch (const std::ios_base::failure&) {
                     }
                 },
diff --git a/src/test/fuzz/rpc.cpp b/src/test/fuzz/rpc.cpp
index b6ecf1c492..73bfb7ff55 100644
--- a/src/test/fuzz/rpc.cpp
+++ b/src/test/fuzz/rpc.cpp
@@ -271,7 +271,7 @@ std::string ConsumeScalarRPCArgument(FuzzedDataProvider& fuzzed_data_provider)
             }
             CDataStream data_stream{SER_NETWORK, PROTOCOL_VERSION};
             data_stream << *opt_psbt;
-            r = EncodeBase64({data_stream.begin(), data_stream.end()});
+            r = EncodeBase64(data_stream);
         },
         [&] {
             // base58 encoded key
diff --git a/src/test/script_tests.cpp b/src/test/script_tests.cpp
index eacd7ae894..88e52fdee7 100644
--- a/src/test/script_tests.cpp
+++ b/src/test/script_tests.cpp
@@ -155,10 +155,10 @@ void DoTest(const CScript& scriptPubKey, const CScript& scriptSig, const CScript
     if (libconsensus_flags == flags) {
         int expectedSuccessCode = expect ? 1 : 0;
         if (flags & bitcoinconsensus_SCRIPT_FLAGS_VERIFY_WITNESS) {
-            BOOST_CHECK_MESSAGE(bitcoinconsensus_verify_script_with_amount(scriptPubKey.data(), scriptPubKey.size(), txCredit.vout[0].nValue, stream.data(), stream.size(), 0, libconsensus_flags, nullptr) == expectedSuccessCode, message);
+            BOOST_CHECK_MESSAGE(bitcoinconsensus_verify_script_with_amount(scriptPubKey.data(), scriptPubKey.size(), txCredit.vout[0].nValue, UCharCast(stream.data()), stream.size(), 0, libconsensus_flags, nullptr) == expectedSuccessCode, message);
         } else {
-            BOOST_CHECK_MESSAGE(bitcoinconsensus_verify_script_with_amount(scriptPubKey.data(), scriptPubKey.size(), 0, stream.data(), stream.size(), 0, libconsensus_flags, nullptr) == expectedSuccessCode, message);
-            BOOST_CHECK_MESSAGE(bitcoinconsensus_verify_script(scriptPubKey.data(), scriptPubKey.size(), stream.data(), stream.size(), 0, libconsensus_flags, nullptr) == expectedSuccessCode, message);
+            BOOST_CHECK_MESSAGE(bitcoinconsensus_verify_script_with_amount(scriptPubKey.data(), scriptPubKey.size(), 0, UCharCast(stream.data()), stream.size(), 0, libconsensus_flags, nullptr) == expectedSuccessCode, message);
+            BOOST_CHECK_MESSAGE(bitcoinconsensus_verify_script(scriptPubKey.data(), scriptPubKey.size(), UCharCast(stream.data()), stream.size(), 0, libconsensus_flags, nullptr) == expectedSuccessCode, message);
         }
     }
 #endif
@@ -1520,7 +1520,7 @@ BOOST_AUTO_TEST_CASE(bitcoinconsensus_verify_script_returns_true)
     stream << spendTx;
 
     bitcoinconsensus_error err;
-    int result = bitcoinconsensus_verify_script(scriptPubKey.data(), scriptPubKey.size(), stream.data(), stream.size(), nIn, libconsensus_flags, &err);
+    int result = bitcoinconsensus_verify_script(scriptPubKey.data(), scriptPubKey.size(), UCharCast(stream.data()), stream.size(), nIn, libconsensus_flags, &err);
     BOOST_CHECK_EQUAL(result, 1);
     BOOST_CHECK_EQUAL(err, bitcoinconsensus_ERR_OK);
 }
@@ -1543,7 +1543,7 @@ BOOST_AUTO_TEST_CASE(bitcoinconsensus_verify_script_tx_index_err)
     stream << spendTx;
 
     bitcoinconsensus_error err;
-    int result = bitcoinconsensus_verify_script(scriptPubKey.data(), scriptPubKey.size(), stream.data(), stream.size(), nIn, libconsensus_flags, &err);
+    int result = bitcoinconsensus_verify_script(scriptPubKey.data(), scriptPubKey.size(), UCharCast(stream.data()), stream.size(), nIn, libconsensus_flags, &err);
     BOOST_CHECK_EQUAL(result, 0);
     BOOST_CHECK_EQUAL(err, bitcoinconsensus_ERR_TX_INDEX);
 }
@@ -1566,7 +1566,7 @@ BOOST_AUTO_TEST_CASE(bitcoinconsensus_verify_script_tx_size)
     stream << spendTx;
 
     bitcoinconsensus_error err;
-    int result = bitcoinconsensus_verify_script(scriptPubKey.data(), scriptPubKey.size(), stream.data(), stream.size() * 2, nIn, libconsensus_flags, &err);
+    int result = bitcoinconsensus_verify_script(scriptPubKey.data(), scriptPubKey.size(), UCharCast(stream.data()), stream.size() * 2, nIn, libconsensus_flags, &err);
     BOOST_CHECK_EQUAL(result, 0);
     BOOST_CHECK_EQUAL(err, bitcoinconsensus_ERR_TX_SIZE_MISMATCH);
 }
@@ -1589,7 +1589,7 @@ BOOST_AUTO_TEST_CASE(bitcoinconsensus_verify_script_tx_serialization)
     stream << 0xffffffff;
 
     bitcoinconsensus_error err;
-    int result = bitcoinconsensus_verify_script(scriptPubKey.data(), scriptPubKey.size(), stream.data(), stream.size(), nIn, libconsensus_flags, &err);
+    int result = bitcoinconsensus_verify_script(scriptPubKey.data(), scriptPubKey.size(), UCharCast(stream.data()), stream.size(), nIn, libconsensus_flags, &err);
     BOOST_CHECK_EQUAL(result, 0);
     BOOST_CHECK_EQUAL(err, bitcoinconsensus_ERR_TX_DESERIALIZE);
 }
@@ -1612,7 +1612,7 @@ BOOST_AUTO_TEST_CASE(bitcoinconsensus_verify_script_amount_required_err)
     stream << spendTx;
 
     bitcoinconsensus_error err;
-    int result = bitcoinconsensus_verify_script(scriptPubKey.data(), scriptPubKey.size(), stream.data(), stream.size(), nIn, libconsensus_flags, &err);
+    int result = bitcoinconsensus_verify_script(scriptPubKey.data(), scriptPubKey.size(), UCharCast(stream.data()), stream.size(), nIn, libconsensus_flags, &err);
     BOOST_CHECK_EQUAL(result, 0);
     BOOST_CHECK_EQUAL(err, bitcoinconsensus_ERR_AMOUNT_REQUIRED);
 }
@@ -1635,7 +1635,7 @@ BOOST_AUTO_TEST_CASE(bitcoinconsensus_verify_script_invalid_flags)
     stream << spendTx;
 
     bitcoinconsensus_error err;
-    int result = bitcoinconsensus_verify_script(scriptPubKey.data(), scriptPubKey.size(), stream.data(), stream.size(), nIn, libconsensus_flags, &err);
+    int result = bitcoinconsensus_verify_script(scriptPubKey.data(), scriptPubKey.size(), UCharCast(stream.data()), stream.size(), nIn, libconsensus_flags, &err);
     BOOST_CHECK_EQUAL(result, 0);
     BOOST_CHECK_EQUAL(err, bitcoinconsensus_ERR_INVALID_FLAGS);
 }
diff --git a/src/test/serialize_tests.cpp b/src/test/serialize_tests.cpp
index e91c203c26..6cc995b16e 100644
--- a/src/test/serialize_tests.cpp
+++ b/src/test/serialize_tests.cpp
@@ -186,76 +186,78 @@ BOOST_AUTO_TEST_CASE(noncanonical)
     std::vector<char>::size_type n;
 
     // zero encoded with three bytes:
-    ss.write("\xfd\x00\x00", 3);
+    ss.write(MakeByteSpan("\xfd\x00\x00").first(3));
     BOOST_CHECK_EXCEPTION(ReadCompactSize(ss), std::ios_base::failure, isCanonicalException);
 
     // 0xfc encoded with three bytes:
-    ss.write("\xfd\xfc\x00", 3);
+    ss.write(MakeByteSpan("\xfd\xfc\x00").first(3));
     BOOST_CHECK_EXCEPTION(ReadCompactSize(ss), std::ios_base::failure, isCanonicalException);
 
     // 0xfd encoded with three bytes is OK:
-    ss.write("\xfd\xfd\x00", 3);
+    ss.write(MakeByteSpan("\xfd\xfd\x00").first(3));
     n = ReadCompactSize(ss);
     BOOST_CHECK(n == 0xfd);
 
     // zero encoded with five bytes:
-    ss.write("\xfe\x00\x00\x00\x00", 5);
+    ss.write(MakeByteSpan("\xfe\x00\x00\x00\x00").first(5));
     BOOST_CHECK_EXCEPTION(ReadCompactSize(ss), std::ios_base::failure, isCanonicalException);
 
     // 0xffff encoded with five bytes:
-    ss.write("\xfe\xff\xff\x00\x00", 5);
+    ss.write(MakeByteSpan("\xfe\xff\xff\x00\x00").first(5));
     BOOST_CHECK_EXCEPTION(ReadCompactSize(ss), std::ios_base::failure, isCanonicalException);
 
     // zero encoded with nine bytes:
-    ss.write("\xff\x00\x00\x00\x00\x00\x00\x00\x00", 9);
+    ss.write(MakeByteSpan("\xff\x00\x00\x00\x00\x00\x00\x00\x00").first(9));
     BOOST_CHECK_EXCEPTION(ReadCompactSize(ss), std::ios_base::failure, isCanonicalException);
 
     // 0x01ffffff encoded with nine bytes:
-    ss.write("\xff\xff\xff\xff\x01\x00\x00\x00\x00", 9);
+    ss.write(MakeByteSpan("\xff\xff\xff\xff\x01\x00\x00\x00\x00").first(9));
     BOOST_CHECK_EXCEPTION(ReadCompactSize(ss), std::ios_base::failure, isCanonicalException);
 }
 
 BOOST_AUTO_TEST_CASE(insert_delete)
 {
+    constexpr auto B2I{[](std::byte b) { return std::to_integer<uint8_t>(b); }};
+
     // Test inserting/deleting bytes.
     CDataStream ss(SER_DISK, 0);
     BOOST_CHECK_EQUAL(ss.size(), 0U);
 
-    ss.write("\x00\x01\x02\xff", 4);
+    ss.write(MakeByteSpan("\x00\x01\x02\xff").first(4));
     BOOST_CHECK_EQUAL(ss.size(), 4U);
 
-    char c = (char)11;
+    uint8_t c{11};
 
     // Inserting at beginning/end/middle:
-    ss.insert(ss.begin(), c);
+    ss.insert(ss.begin(), std::byte{c});
     BOOST_CHECK_EQUAL(ss.size(), 5U);
-    BOOST_CHECK_EQUAL(ss[0], c);
-    BOOST_CHECK_EQUAL(ss[1], 0);
+    BOOST_CHECK_EQUAL(B2I(ss[0]), c);
+    BOOST_CHECK_EQUAL(B2I(ss[1]), 0);
 
-    ss.insert(ss.end(), c);
+    ss.insert(ss.end(), std::byte{c});
     BOOST_CHECK_EQUAL(ss.size(), 6U);
-    BOOST_CHECK_EQUAL(ss[4], 0xff);
-    BOOST_CHECK_EQUAL(ss[5], c);
+    BOOST_CHECK_EQUAL(B2I(ss[4]), 0xff);
+    BOOST_CHECK_EQUAL(B2I(ss[5]), c);
 
-    ss.insert(ss.begin()+2, c);
+    ss.insert(ss.begin() + 2, std::byte{c});
     BOOST_CHECK_EQUAL(ss.size(), 7U);
-    BOOST_CHECK_EQUAL(ss[2], c);
+    BOOST_CHECK_EQUAL(B2I(ss[2]), c);
 
     // Delete at beginning/end/middle
     ss.erase(ss.begin());
     BOOST_CHECK_EQUAL(ss.size(), 6U);
-    BOOST_CHECK_EQUAL(ss[0], 0);
+    BOOST_CHECK_EQUAL(B2I(ss[0]), 0);
 
     ss.erase(ss.begin()+ss.size()-1);
     BOOST_CHECK_EQUAL(ss.size(), 5U);
-    BOOST_CHECK_EQUAL(ss[4], 0xff);
+    BOOST_CHECK_EQUAL(B2I(ss[4]), 0xff);
 
     ss.erase(ss.begin()+1);
     BOOST_CHECK_EQUAL(ss.size(), 4U);
-    BOOST_CHECK_EQUAL(ss[0], 0);
-    BOOST_CHECK_EQUAL(ss[1], 1);
-    BOOST_CHECK_EQUAL(ss[2], 2);
-    BOOST_CHECK_EQUAL(ss[3], 0xff);
+    BOOST_CHECK_EQUAL(B2I(ss[0]), 0);
+    BOOST_CHECK_EQUAL(B2I(ss[1]), 1);
+    BOOST_CHECK_EQUAL(B2I(ss[2]), 2);
+    BOOST_CHECK_EQUAL(B2I(ss[3]), 0xff);
 }
 
 BOOST_AUTO_TEST_CASE(class_methods)
diff --git a/src/test/streams_tests.cpp b/src/test/streams_tests.cpp
index 3571927397..a8f6cdd4a0 100644
--- a/src/test/streams_tests.cpp
+++ b/src/test/streams_tests.cpp
@@ -160,7 +160,7 @@ BOOST_AUTO_TEST_CASE(bitstream_reader_writer)
 
 BOOST_AUTO_TEST_CASE(streams_serializedata_xor)
 {
-    std::vector<uint8_t> in;
+    std::vector<std::byte> in;
     std::vector<char> expected_xor;
     std::vector<unsigned char> key;
     CDataStream ds(in, 0, 0);
@@ -174,8 +174,8 @@ BOOST_AUTO_TEST_CASE(streams_serializedata_xor)
             std::string(expected_xor.begin(), expected_xor.end()),
             ds.str());
 
-    in.push_back('\x0f');
-    in.push_back('\xf0');
+    in.push_back(std::byte{0x0f});
+    in.push_back(std::byte{0xf0});
     expected_xor.push_back('\xf0');
     expected_xor.push_back('\x0f');
 
@@ -195,8 +195,8 @@ BOOST_AUTO_TEST_CASE(streams_serializedata_xor)
 
     in.clear();
     expected_xor.clear();
-    in.push_back('\xf0');
-    in.push_back('\x0f');
+    in.push_back(std::byte{0xf0});
+    in.push_back(std::byte{0x0f});
     expected_xor.push_back('\x0f');
     expected_xor.push_back('\x00');
 
diff --git a/src/uint256.h b/src/uint256.h
index 72681d09c9..5c3a2f5409 100644
--- a/src/uint256.h
+++ b/src/uint256.h
@@ -6,6 +6,8 @@
 #ifndef BITCOIN_UINT256_H
 #define BITCOIN_UINT256_H
 
+#include <span.h>
+
 #include <assert.h>
 #include <cstring>
 #include <stdint.h>
@@ -96,13 +98,13 @@ public:
     template<typename Stream>
     void Serialize(Stream& s) const
     {
-        s.write((char*)m_data, sizeof(m_data));
+        s.write(MakeByteSpan(m_data));
     }
 
     template<typename Stream>
     void Unserialize(Stream& s)
     {
-        s.read((char*)m_data, sizeof(m_data));
+        s.read(MakeWritableByteSpan(m_data));
     }
 };
 
diff --git a/src/validation.cpp b/src/validation.cpp
index cb2b60b481..b01ad2b2b8 100644
--- a/src/validation.cpp
+++ b/src/validation.cpp
@@ -4442,7 +4442,7 @@ void CChainState::LoadExternalBlockFile(FILE* fileIn, FlatFilePos* dbp)
             try {
                 // locate a header
                 unsigned char buf[CMessageHeader::MESSAGE_START_SIZE];
-                blkdat.FindByte(char(m_params.MessageStart()[0]));
+                blkdat.FindByte(m_params.MessageStart()[0]);
                 nRewind = blkdat.GetPos() + 1;
                 blkdat >> buf;
                 if (memcmp(buf, m_params.MessageStart(), CMessageHeader::MESSAGE_START_SIZE)) {
diff --git a/src/wallet/bdb.cpp b/src/wallet/bdb.cpp
index 5b264ac4ad..88969afbce 100644
--- a/src/wallet/bdb.cpp
+++ b/src/wallet/bdb.cpp
@@ -680,10 +680,10 @@ bool BerkeleyBatch::ReadAtCursor(CDataStream& ssKey, CDataStream& ssValue, bool&
     // Convert to streams
     ssKey.SetType(SER_DISK);
     ssKey.clear();
-    ssKey.write((char*)datKey.get_data(), datKey.get_size());
+    ssKey.write({BytePtr(datKey.get_data()), datKey.get_size()});
     ssValue.SetType(SER_DISK);
     ssValue.clear();
-    ssValue.write((char*)datValue.get_data(), datValue.get_size());
+    ssValue.write({BytePtr(datValue.get_data()), datValue.get_size()});
     return true;
 }
 
@@ -755,7 +755,7 @@ bool BerkeleyBatch::ReadKey(CDataStream&& key, CDataStream& value)
     SafeDbt datValue;
     int ret = pdb->get(activeTxn, datKey, datValue, 0);
     if (ret == 0 && datValue.get_data() != nullptr) {
-        value.write((char*)datValue.get_data(), datValue.get_size());
+        value.write({BytePtr(datValue.get_data()), datValue.get_size()});
         return true;
     }
     return false;
diff --git a/src/wallet/dump.cpp b/src/wallet/dump.cpp
index 645576ef91..b9b8b9f783 100644
--- a/src/wallet/dump.cpp
+++ b/src/wallet/dump.cpp
@@ -46,12 +46,12 @@ bool DumpWallet(CWallet& wallet, bilingual_str& error)
     // Write out a magic string with version
     std::string line = strprintf("%s,%u\n", DUMP_MAGIC, DUMP_VERSION);
     dump_file.write(line.data(), line.size());
-    hasher.write(line.data(), line.size());
+    hasher.write(MakeByteSpan(line));
 
     // Write out the file format
     line = strprintf("%s,%s\n", "format", db.Format());
     dump_file.write(line.data(), line.size());
-    hasher.write(line.data(), line.size());
+    hasher.write(MakeByteSpan(line));
 
     if (ret) {
 
@@ -72,7 +72,7 @@ bool DumpWallet(CWallet& wallet, bilingual_str& error)
             std::string value_str = HexStr(ss_value);
             line = strprintf("%s,%s\n", key_str, value_str);
             dump_file.write(line.data(), line.size());
-            hasher.write(line.data(), line.size());
+            hasher.write(MakeByteSpan(line));
         }
     }
 
@@ -149,7 +149,7 @@ bool CreateFromDump(const std::string& name, const fs::path& wallet_path, biling
         return false;
     }
     std::string magic_hasher_line = strprintf("%s,%s\n", magic_key, version_value);
-    hasher.write(magic_hasher_line.data(), magic_hasher_line.size());
+    hasher.write(MakeByteSpan(magic_hasher_line));
 
     // Get the stored file format
     std::string format_key;
@@ -180,7 +180,7 @@ bool CreateFromDump(const std::string& name, const fs::path& wallet_path, biling
         warnings.push_back(strprintf(_("Warning: Dumpfile wallet format \"%s\" does not match command line specified format \"%s\"."), format_value, file_format));
     }
     std::string format_hasher_line = strprintf("%s,%s\n", format_key, format_value);
-    hasher.write(format_hasher_line.data(), format_hasher_line.size());
+    hasher.write(MakeByteSpan(format_hasher_line));
 
     DatabaseOptions options;
     DatabaseStatus status;
@@ -219,7 +219,7 @@ bool CreateFromDump(const std::string& name, const fs::path& wallet_path, biling
             }
 
             std::string line = strprintf("%s,%s\n", key, value);
-            hasher.write(line.data(), line.size());
+            hasher.write(MakeByteSpan(line));
 
             if (key.empty() || value.empty()) {
                 continue;
diff --git a/src/wallet/sqlite.cpp b/src/wallet/sqlite.cpp
index 3bea0de99f..c893307127 100644
--- a/src/wallet/sqlite.cpp
+++ b/src/wallet/sqlite.cpp
@@ -394,9 +394,9 @@ bool SQLiteBatch::ReadKey(CDataStream&& key, CDataStream& value)
         return false;
     }
     // Leftmost column in result is index 0
-    const char* data = reinterpret_cast<const char*>(sqlite3_column_blob(m_read_stmt, 0));
-    int data_size = sqlite3_column_bytes(m_read_stmt, 0);
-    value.write(data, data_size);
+    const std::byte* data{BytePtr(sqlite3_column_blob(m_read_stmt, 0))};
+    size_t data_size(sqlite3_column_bytes(m_read_stmt, 0));
+    value.write({data, data_size});
 
     sqlite3_clear_bindings(m_read_stmt);
     sqlite3_reset(m_read_stmt);
@@ -511,12 +511,12 @@ bool SQLiteBatch::ReadAtCursor(CDataStream& key, CDataStream& value, bool& compl
     }
 
     // Leftmost column in result is index 0
-    const char* key_data = reinterpret_cast<const char*>(sqlite3_column_blob(m_cursor_stmt, 0));
-    int key_data_size = sqlite3_column_bytes(m_cursor_stmt, 0);
-    key.write(key_data, key_data_size);
-    const char* value_data = reinterpret_cast<const char*>(sqlite3_column_blob(m_cursor_stmt, 1));
-    int value_data_size = sqlite3_column_bytes(m_cursor_stmt, 1);
-    value.write(value_data, value_data_size);
+    const std::byte* key_data{BytePtr(sqlite3_column_blob(m_cursor_stmt, 0))};
+    size_t key_data_size(sqlite3_column_bytes(m_cursor_stmt, 0));
+    key.write({key_data, key_data_size});
+    const std::byte* value_data{BytePtr(sqlite3_column_blob(m_cursor_stmt, 1))};
+    size_t value_data_size(sqlite3_column_bytes(m_cursor_stmt, 1));
+    value.write({value_data, value_data_size});
     return true;
 }